Soil and vegetation sampling during the early stage of Fukushima Daiichi Nuclear Power Plant accident and the implication for the emergency preparedness for agricultural systems

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Highlights

  • The sampling protocols applied just after the FDNPP accident have been reviewed and the protocols for emergency the soil and vegetation sampling were proposed.

  • As a result of Fukushima's outcome, vegetation sampling will be recommended when the additional dose rate (above background) is higher than 0.1 μSv/h.

  • Predetermined sampling points for soil and vegetation sampling and measurement exercises are highly recommended.

Abstract

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, immediate soil and vegetation sampling were conducted according to the action plan of nuclear emergency monitoring; however, analysing the monitoring dataset was difficult because the sampling protocols were not standardised. In this study, the sampling protocols applied just after the FDNPP accident were reviewed, and the monitoring data were analysed. The detailed protocols and results can provide a sound basis for guidelines of soil and vegetation sampling for nuclear emergency monitoring. The activity concentrations of 137Cs and 131I in weed samples measured immediately after the FDNPP accident were related to the air dose rate at 1 m. Consequently, vegetation sampling is recommended when the additional dose rate (above background) is higher than 0.1 μSv/h. To enhance the efficiency of a protective response in the case of a nuclear accident, predetermined sampling points for soil and vegetation sampling should be considered in the preparedness plan for nuclear emergencies. Furthermore, sampling and analytical measurement capacities (time, people, cost) during the early phase after nuclear emergencies need to be considered in the preparedness and action plan, and sampling and measurement exercises are highly recommended.

Introduction

After a nuclear emergency, to protect the public from external and internal radiation, performing immediate sampling and radioactivity measurements to determine the contamination levels of the soil and vegetation is advisable (IAEA, 1999). Possible consumption restrictions of agricultural products based on measurement results can be implemented. For example, short-lived 131I is radiotoxic to humans because it may accumulate in the thyroid and cause thyroid cancer (Baverstock et al., 1992). Therefore, it is essential to measure 131I within a few days. If the activity concentration is expected to exceed the intervention criteria for food consumption, the agricultural products should be banned immediately. For this purpose, it is necessary to establish emergency sampling protocols and sample analysis capacity within a limited time frame. For quick monitoring in case of an accident, it is necessary to establish well-designed emergency monitoring systems.

As part of a regulatory protocol, environmental monitoring networks have been established in most countries with nuclear facilities. Such monitoring networks often combine off-line sampling and analysis programs (measurements of radioactivity) with an on-line gamma dose rate and air concentration network, which can act as an early warning system in the case of an accident. The online monitoring network is one of the primary data sources for decision-making during the radioactivity release phase of an accident. Meanwhile, sampling and measurement programs that commence just after the release would provide valuable supplementary information. International agencies, such as the IAEA, have issued guidelines (IAEA, 1999) on sampling and analysis in the case of a nuclear emergency. Thus far, there have been very few actual events to test the emergency response of the monitoring networks. In addition, modification of sampling methodologies may be required over time, from days and weeks to months because the monitoring objectives change. Therefore, improving and optimising the sampling and monitoring of the soil and food while creating general guidelines for monitoring radioactivity in food and agriculture is necessary (Dercon et al., 2020). In this study, the focus is directed toward the early transition phase of a nuclear emergency, starting from a few days to a few weeks after release. During the first stage of a nuclear accident, direct deposition to vegetables is the main contamination pathway when crops are in the field during the release (Pröhl, 2009), whereas root uptake will become the main pathway in the following year. The prognosis of the contamination of food, amount of radionuclides, and their spectra in the soil requires soil and vegetation monitoring data.

In Japan, after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the Emergency Operation Center (EOC) performed operations at the Environmental Radioactivity Monitoring Center of Fukushima (ERMF), collecting soil and vegetation samples (MEXT, 2011a,b). The measurement results were published one day after the major release on March 15 (Katata et al., 2015). Although these data were essential for immediately estimating the radioactivity contamination, interpreting the deposition density of 134Cs, 137Cs, and 131I in the soils (given in Bq/m2) was challenging because the data are provided in the units of (Bq/kg). For the vegetation sampling results, detailed protocols have not been established; thus, it is difficult to properly analyse the dataset. The use of standardised protocols, analytical methods, and communication is essential for applying the lessons learned from the Fukushima accident.

The selection of sampling locations is also essential in the implementation of nuclear emergency monitoring. For vegetation sampling, it is necessary to select optimal locations for sampling and apply appropriate methods for reporting and visualising sample locations in further data analysis. In the case of the Japanese emergency monitoring plan, no map-based dataset of food and vegetables has been developed; only the names of the cities, towns, etc. have been recorded. For example, in Fukushima, the areas of these municipalities range from 16 to 1272 km2 (Kato and Onda, 2018); thus, estimating the degree of radioactivity contamination after a nuclear emergency based on this geographical information is difficult. Meanwhile, other countries, such as Belgium, have well-defined sampling protocols. By combining the lessons learned from the FDNPP accident with protocols of other countries, we can improve and optimise the guidelines for monitoring radioactivity during an emergency period.

In this study, based on the experience of emergency monitoring immediately after the FDNPP accident in Fukushima and the present monitoring programme in the Belgian emergency preparedness and action plan, the method and applicability of emergency protocols are discussed for the radioactivity monitoring of foods and agricultural products during a nuclear emergency period.

Section snippets

Emergency vegetation sampling conducted in the FDNPP accident

Initially, the Fukushima Off-Site Center was established in Okuma Town, within 10 km of the FDNPP. The off-site centre was located within the evacuation zone and then moved to Fukushima city on March 14, 2011. The emergency plan contained pre-determined sampling points within a 10 km radius; however, there were no predetermined sampling points outside of 10 km from the FDNPP. Consequently, sampling points outside of the 10 km radius from the FDNPP had to be selected on March 15, comprising

Dose rate and activity concentration of 131I in the vegetation samples

During the first days after the Fukushima accident, short-lived radioisotopes, such as 132Te and 132I, accounted for nearly 49% of the deposit activity (Champion et al., 2013). Afterwards, 134Cs and 131I became the primary source of radiation. For grass samples, the direct deposition of the fallout on the vegetation can result in the relatively high activity concentrations of these radionuclides in feed and foods (Pröhl, 2009).

The activity concentrations of 137Cs and 131I in vegetation versus

Conclusion

Soil sampling approaches for analysing the radioactivity concentration in the soil and fallout on the farmland and the soil and vegetation sampling methods recommended during a nuclear emergency response are described. After the FDNPP accident, immediate soil and vegetation sampling were conducted; however, the detailed protocols were not shown, which made it difficult to analyse the monitoring dataset. In this study, the sampling protocols applied just after the FDNPP were reviewed, and data

Declaration of competing interest

No conflict of Interest of this paper.

Acknowledgment

This paper is supported by the IAEA CRP D15015.

References (34)

  • U. Barnekov et al.

    Guidelines on Soil and Vegetation Sampling for Radiological Monitoring Purposes

    (2019)
  • K. Baverstock et al.

    Thyroid cancer after Chernobyl

    Nature

    (1992)
  • D. Champion et al.

    The IRSN's earliest assessments of the Fukushima accident's consequences for the terrestrial environment in Japan

    Radioprotection

    (2013)
  • Fesenko, S., Onda, Y., Shinano, T., Dercon, G. (in this issue) Comparative analysis of the dynamics of radionuclide...
  • IAEA

    Generic Procedures for Monitoring in a Nuclear or Radiological Emergency

    (1999)
  • IAEA

    Criteria for Use in Preparedness and Response for a Nuclear or Radiological Emergency IAEA Safety Standards Series No. GS-G-2

    (2011)
  • IAEA

    Operational Intervention Levels for Reactor Emergencies

    (2017)
  • Cited by (6)

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